News

February 2005. A bug is fixed in the version of RhicBos posted here. The bug affects lepton angular distributions in W- boson production (including d(sigma)/dye), but does not affect pT distributions or W+ and Z0 production. In the first approximation, the correction results  in the interchange  ye  <-> -ye in the lepton rapidity distribution.


What is RhicBos?

RhicBos is a specialized Monte-Carlo integration program that calculates resummed differential distributions of heavy lepton pairs produced in hadron-hadron collisions. It is written on the basis of the Monte-Carlo program ResBos, and it is optimized for polarized proton-proton collisions at the Relativistic Heavy Ion Collider.

Who are the authors of RhicBos?

RhicBos is written by
  • Pavel Nadolsky (HEP Theory, Argonne National Laboratory), in collaboration with
  • C.-P. Yuan (Department of Physics & Astronomy, Michigan State University)
The contact person is
Pavel Nadolsky
E-mail: nadolsky at hep.anl.gov
HEP 362                     
Argonne National Laboratory
Argonne, IL 60439-4815,
U.S.A.

Phone: (630) 252-6965
Fax:     (630) 252-5047

RhicBos references

  1. P. M. Nadolsky and C.-P. Yuan, Soft parton radiation in polarized vector boson production: theoretical issues, Nucl.Phys. B666, 3 (2003), hep-ph/0304001
  2. P. M. Nadolsky and C.-P. Yuan, Single-spin physics with W bosons at RHIC, Nucl.Phys. B666, 31 (2003), hep-ph/0304002; the source and postscript of the version with high-resolution figures

What  is the difference between RhicBos and other Monte-Carlo integration programs?

In order to describe lepton differential distributions correctly, the finite-order QCD cross sections must be combined with the all-order sum of leading logarithmic terms, which contribute at small transverse momenta of vector bosons. RhicBos calculates such resummed cross sections using the formalism by Collins, Soper, and Sterman [Nucl. Phys., B250, 199 (1985)] and consistently generates a variety of differential distributions at the lepton level.  Therefore, RhicBos output contains all information from the finite-order cross section and, in addition, it includes the leading contributions from all orders of the strong coupling in the small transverse momentum region.

Which processes are currently implemented?

RhicBos calculates all processes that are implemented in the unpolarized version of the program (ResBos). In addition, it calculates the resummed cross sections for arbitrary polarizations of the initial-state hadrons in
  • W boson production pp -> W X -> e nu X
  • Z0 boson production pp -> Z0 X -> e ebar X
  • Drell-Yan pair production pp ->  gamma X -> e ebar X

How does RhicBos work?

  • RhicBos reads in the small-QT resummed cross sections (W-terms) and regular pieces (Y-terms) calculated on a grid of points in the invariant mass Q, rapidity y, and transverse momentum QT of the vector boson
  • It adds the W-terms to the  Y-term to obtain the resummed cross section in the full range of QT
  • To improve the description of the large QT  region, it determines the procedure for switching from the W+Y cross section to the NLO cross section at QT~Q
  • It interpolates the matched grids to find the cross sections at any point in Q, y, and QT
  • It then integrates the interpolated cross sections over the available phase space with the help of the  VEGAS multidimensional integration routine

How do I run RhicBos?

RhicBos is publicly available in the form of the  Fortran code. It can be compiled on a UNIX system with the help of the included Makefile. The input cross section grids for RhicBos can also be downloaded from this website.

RhicBos must be linked to CERN libraries PACKLIB and KERNLIB, which are available here.

How does the output from RhicBos look like?

RhicBos can produce the output in a variety of formats, including GBOOK (simple numerical format), as well as HBOOK and NTUPLE (which can be then analyzed with the help of the Physics Analysis Workstation (PAW)).

What is the soft gluon resummation?

Soft gluon resummation is a method for organization of calculations in perturbative Quantum Chromodynamics based on a special factorization theorem for transverse momentum distributions. Please see a simple  explanation of the resummation formalism and interactive plotter of resummed  cross sections.